93 bouncing speedo

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TechNova

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Many years ago, my 88 had a intermitent bouncing speedo. The ground wire at the thermostat housing was off. I had changed thermostat and failed to put the wire back on.
Have you worked on something right before the problem started?
 

Sparkysikes

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Maybe 6 months ago it started. I did the auto swap about 18 months ago. My thoughts were a ground due to cruise causing it to bounce I just don't know where to start. I've had 2 VSS modules. I regeared and installed a variable VSS. But same problem between the 2 VSS.

Good note is that when the speedo lurches the rpms don't so I don't think. I have to worry about trans!
 

someotherguy

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My '92 used to do it when I was going highway speed and hit the turn signals, the speedometer would dip way down then snap back to where it was. It's been -forever- since I researched this problem but my very vague memory of it was there was a TSB about adding a small capacitor to the gauge cluster circuit board to act as a buffer; good luck finding that info but I also seem to recall it resulted in a design change later. I wouldn't suggest based on my super vague memory that you run out and buy another cluster but IF you have easy access to say one from a '94 it might be worth trying just on a whim.

Also as TechNova said check all your grounds particularly the ones at, and next to, the thermostat housing...make sure they're top notch. Also your gauge cluster grounds on the metal tab that your ALDL (diag) connector is attached to, so check/clean that one up, too. Single black wire with a ring terminal.

If all else fails it may be your speed sensor in the transmission tailshaft housing.

Richard
 

gearheadE30

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There is a large common ground under the dash as well that ties everything together to one of the dash braces. I eventually traced some of my odd gauge issues back to that ground coming loose.
 

someotherguy

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Enormous wiring difference between a 1993 and a 1998 (or that 2000 Tahoe Ltd).. they're not even close to the same, so anything he recalls from his will be mostly irrelevant, if they're regarding the trucks in his sig.

Richard
 
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